Telephone switching apparatus



J. L. McQUARRIL TEL'EPHONE SWITCHING APPARATUS.

APPLICATION FILED MAYl3,,I9I8.

1,376,893. Patented M y 3, 1921.

elements, such as the contact brushes, which UNITED STTES PATENT OFFIQE.

JAMES L. MCQUABRIE, OF MONTCLAIR, NEW JERSEY, ASSIGNOR TO WESTERN ELEC-TRIO COMPANY, INCORPORATED, OF NEW YORK, N. Y., A CORPORATI OF v YORK.

' Application filed May 13,

To all whom it may concern I Be it known that I, JAMEs L. MGQUARRIE, acitizen of the United States, residing at Montclair, in the county ofEssex, State of New Jersey, have invented certain new and usefulImprovements in Telephone Switching Apparatus, of which the following isa full, clear, concise, and exact description.

This invention relates to automatic telephone exchange systems, andparticularly to a novel arrangement in the construction and operation ofthe switching apparatus used therein for establishing conversationalconnections between subscribers lines.

It is the customary practice in automatic telephone systems to arrangethe subscribers lines and the switches used for interconnecting the samein groups, each group and the subdivisions thereof being arbitrarilyassigned a suitable numerical designation. Where all switches of a.group, whether finders, selectors or connectors, are common to the useof all lines in one or more groups of lines, it is necessary to provideas many switches to serve a group of lines as is required to handle thelargest number of simultaneous calls that is expected to arise in suchgroup. Experience shows that in systems operating under the averagetraffic conditions, the maximum number of calls likely to appear in agroup is about ten per cent. of the number of lines in the group.

Considering the type of selective switches generally used heretofore inautomatic telephone systems in which the selectively controlled movableelement, as the switch shaft, has fixed thereto and movable therewithform an actual part of the conversational circuit established, it isseen that on the above assumed basis of trafiic it-'becomes necessary toemploy ten switches to serve a group of one hundred lines. VVhena callis initiated, one of the switches will be-operated to its set positionto extend the connection and will remain in this position until theconversation has been terminated. On the occurrence of a second call inthe same group, one of the nine remaining switches is similarly operatedand held in use to the exclusion of other lines during theconversational period, and hence where switches of this type are usedthe necessity Specification of Letters Patent.

TELETHONE SWITCHING APPARATUS.

v Patented May 31921. 1918. Serial No. 234,180. 7

of employing ten switches to give ,a certain group of one hundred linesa proper grade of 'serv1ce,'results not only from the fact that a switchmust beheld to the exclusive use of the calling line during theconnecting period, but also from the more important fact that the switchmust be maintained busy and non-available to other lines during theentire talking period. This is true since, as above stated, the switchafter having performed its primary function of selecting the desiredcircuit must remain out of use durmg the talking period merely becausethe directively controlled movable. part of the switch carries elementswhich are essential to the maintenance of the connection established.

In view of the foregoing, this invention 7 has as its general object,the provision of a switch which may be .directively. operated to selectthe proper circuit in a vdesired numerical group, effect the necessaryconnections with such circuit, and thereupon restore immediately to itsnormal position where it again becomes available to all other lines inthe group. By this means the busy period of the switch is greatlyreduced with the result that the number of switches needed to afford agroup of lines a given grade of service may likewise be reduced.

A feature of the invention consists in a novel arrangement of thecontact bank whereby a plurality of incoming circuits are arranged tohave a crossing or intersect ing point with each of a plurality ofoutgoing circuits, together with means such as deposit members providedat each of the intersecting points, and which serve, when operated, toeffect a connection between the view of a switch embodying thisinvention showing a portion of the contact bank, together with theswitch operating mechanism; Fig. 2 is a side view of the switch, certainparts being removed to afford a clearer understanding of the operation;Fig. 3 is a bottom plan view illustratingthe releasing mechanism; Fig. 4is. an enlarged cross-sectional detail showing the relative arrangementof some of the operating parts; Fig. 5 is an enlarged detail inperspective showing the manner of controlling the sliding bar whichoperates the plunger for depositing a contact making member; and Fig. 6is an enlarged view in perspective showing one of the deposit membersand the circuit contact springs which it controls.

lVhile the principle of this invention is adapted to any class ofautomatic telephone switch it will be considered for the purpose of thepresent discussion as embodied in a selector switch, the function ofwhich is to connect incoming trunks from finders or other selectors totrunks outgoing in the proper "direction to selector or connectorswitches. I

Referring to the drawing, there is shown in Figs. 2, 3 and 6 themannerin which the incoming and outgoing trunk circuits are arranged in thecontact bank. There are ten incoming two-conductor trunk circuits 1, 1,arranged in a plane surface, and disposed along the arcs of concentriccircles. Arranged in a plane immediately below that of trunks 1, 1 is aplurality of outgoing two-conductor trunk circuits 2, 2. The trunks 2,2each extend radially toward the common center of the arcs of trunks 1,1, whereby each of the incoming trunks 1.1 has an intersection or acrossing point with each of the outgoing trunks 2, 2. Preferably theoutgoing trunks 2, 2 comprisev a total of one hundred circuits, whichmay be divided into ten groups of ten trunks each, each of thesuccessive groups consist ing of ten adjacent trunks 2, 2, and occupyinga portion or sector of the contact bank. With this arrangement any oneof the ten incoming trunks 1, 1 has a crossingpoint with each of thetrunksof ten groups of outgoing trunks 2, 2. Each of the incomingcircuits 1, 1 is provided, at the points whereit crosses the outgoing.circuits 2, 2, with spring contact members 3 and 4. Likewise theoutgoing trunks 2, 2 are provided at these points of crossing withcontact springs 5 and 6. The springs 3, 4, 5 and 6 are firmly secured toan insulating supporting plate 7 with their free ends extending upwardinto a position to cooperate with each other, as best seen in Figs. 2and 6. Slidably mounted in plate 7 at the points of intersection are thedeposit pins 8, 8. The pins 8 areprovided with cam gage the lower notchin cam 9, whereby said springs are out of contact with springs 5 and 6.When, however, pin 8 is deposited and assumes its lower position withthe upper notch thereof in engagement with springs 3 and 4 said springsare flexed into contact with outer springs 5 and 6 respectively. Toeconomize in space, the springs 5 and 6 are arranged to be en gaged bysprings 3 or 4, as the case may be, at two adjacent radial positions inthe bank as shown in Fig. 2. In this way the springs 5 and 6 of one setmay be common to two different trunk intersecting points.

A description will next be given of the step -bystep impulse operatedswitching mechanism, which cooperates with the contact bank to firstselect a group of incoming and outgoing trunk intersecting points,thento select a single row of intersections of an idle outgoing trunk withthe incoming trunks, then to select the intersection of this chosenoutgoing trunk with a particular one of the incoming trunks, and lastlyto deposit the pin 8 at such intersection. Rotatably mounted in theupper shelf 10 of supporting frame 29 is a gear member 11, provided atits upper end with gear teeth 12, and at its intermediate portion withan enlargement 14, around the periphery of which gear teeth 13 arearranged. Interposed between the enlargement 14 and the upper surface ofshelf 10 is a ratchet wheel 15 which is journaled for rotation aboutmember 11 as a bearing, and which also serves as a guide or stop' tolimit member 11 against downward movement. threaded on the lower end ofmember 11 retains the same against displacement in the opposite verticaldirection. Supported on the upper surface of the enlargement 14, andiournaled for rotation about gear memher 11, is a combined plunger barcarriage and gear member 17 A nut 1.8 screwed upon a threaded portion ofmember 11 holds carriage 17 in proper vertical 'alinement. The carriage17 is in general of a circular shape, its largest portion being providedwith peripheral teeth to form the ratchet wheel 19. Just below ratchetwheel. 19, the

carriage 17 has its diameter considerably reduced, the reduced portionso formed being provided with gear teeth 20.

The carriage 17 is also provided with a rectangular boss 21 which risesabove the ratchet wheel 19, and is located to one side of the centerthereof, Fig. 1. Boss 21 has extending longitudinally therethrough arectangular slot or channel 22, in which there is slidably mounted aplunger carrying bar A nut 16" 23. A plunger 24 is mounted on theworking end of bar 23, a bracket 25 serving as a guide therefor, while acoiled spring 26 acts to normally retain the plunger in the positionshown. On the other end of bar 23 is cut a series of teeth 27 whichconstantly engage the gear teeth 12 on member 11. A coiled spring 28,one end of which is attached to bar 23, and the other end to boss 21,exerts its tension to hold the plunger bar in its normal innermostposition, as seen in Figs. 1 and 2. By this arrangement when thecarriage is held stationary with respect to the switch frame, and member11 rotated about its axis, the gear teeth 12, meshing with teeth 27cause bar 23 .to be thrust radially outward to carry plunger 24 over thedeposit pins 8 in the contact bank. Also mounted on the supporting shelf10 is a ratchet wheel 30 and a gear wheel 31 which are preferably formedintegral with each other. These wheels are rotatably supported on a stud32, and are held in position by a nut hen assembled on its bearing stud32, the gear wheel 31 is adapted to mesh with teeth 20 on gear member11. A clock spring 34, one end of which is fastened to ratchet wheel 30,and the other end to shelf 10, acts through gears 31 and 20 to maintainthe carriage '17 and its plunger bar 23 in their normal rotary positionwith respect to the contact bank, as seen in Fig. 1.

Mounted at suitable locations on the shelf 10 of frame 29, as shown inFig. 1 of the drawing, are the primary, secondary and tertiary operatinelectromagnets 35, 36 and 37 respectively. 1 agnet 35 is provided withan armature 38 having a pivoted pawl 39 arranged to engage the longtooth ratchet wheel 30, which operates through gears 31 and 20 to rotatecarriage 17 and plunger bar 23 by long steps in a clockwise direction asviewed from the top. Each one of these lon steps advances the plunger 24through an arc corresponding to a numerical group of one hundred trunkintersecting points, or in otherwords, through an arc comprising tenradial rows of deposit pins 8. Magnet 36 is provided with an armature 40having a pawl 41 which-engages the short tooth ratchet wheel 19v torotate the plunger bar 23 by short steps in a clockwise direction. Eachshort stop serves to advance plunger 24 through an arc corresponding'tothe distance between two consecutive radial rows of trunk intersectionpoints. The tertiary magnet 37 is equipped with an armature 42 having apivoted pawl which is arranged to engage and rotate the ratchet wheel15. spring held pawl 44 is pivoted on ratchet wheel 15, and cooperateswith gear teeth 13 on member 11 in such a manner that when magnet 27steps ratchet 15 in a clockwise directicn, the pawl 44 engages teeth 13to im- Par a'sira rot tion to the member 11.

Rotation of gear member 11 operates as above described to advanceplunger 24 radially through the distance corresponding .to

two circular rows of pins 8 for each step of the magnet 37 I Coming nowto a discussion of the mannor in which the plunger 24 is operated todeposit the pin '8 at a selected trunk crossing point there isseen inFig. 5, a detailed showing of the mechanism for accomplishing thispurpose. The boss 21 is provided with twolugs-45 which support arotatable pivot pin 46. A yoke piece 47 is securely mounted on pin 46,and at its upper endis pivotally attached to the hollow guide andsupporting block 48. A plunger'operating bar 49 is pivoted at one end toan arm of the bell crank lever 95. The lever 95 is pivotally secured tobar 23with theother arm thereof extending into operative relation toplunger 24. The plunger operating bar 49 is disposed parallel tobar 23,its free end being guided by and slidably supported in the hollow block48. By this arrangement the bar 49, which is'forced to participate inthe thrusting movement of bar 23, slides through the block 48 a distancecorrespond, ing to the number of steps taken in the'tertiary operationof the mechanism. Thebar 49 is provided with a series of notches 50, onefor each circular row of pins 8. A

spring catch 51 secured to block 48 con 'member 56. A spring 57 actingbetween the frame and member 56 serves to hold rod 54 and lever 52 inthe lowermost position, thus preventing the spring catch 51 fromengaging notches 50. The bell crank member 56 also carries the armatureof an electromagnet 58. which magnet when energized forces rod54 upwardto permit catch 51 to engage a notch 50 in bar 49 for a purpose to bemore fully explained hereinafter A release magnet 59 is provided with anarmature 60which controls a pair of holding dogs 61 and 62. These dogsengage re.- spectively the ratchets 15 and 1.9 to hold the switchmechanism in its advanced position.

In order to restore to normal a deposited pin 8, and thus disconnect thetwo trunk circuits concerned, mechanism about to be described isarranged to be operated-step by step to pick outthe radial row of pinscon taining theone desired to be restored, and

going trunk 2 with the ten incoming trunks 1, 1, and normally rests in ahorizontal plane just below the lower ends of deposit pins 8. A pin 75has its lower end pivoted to pro jection 76 on rod 7 3. and extends upthrough the ratchets 66 and 65 to pivotally engage the tail piece 77 ofarmature 78. A spring 7 9 normally holds pin 75 and rod 7 3 in theposition shown, but when the magnet 80 is energized to attract armature78, rod 73 is rotated in its supporting lugs 71 and 72.

'Rod 73 rotates the apron 74 into engagement with the particular pin 8that is depressed and restores the same to normal.

Mounted on the under side of shelf 64 are the stepping magnets 67 and68. Magnet 67 has an armature 69 and pawl 70 adapted to engage ratchetwheel 65 to rotate the rod 73 in a counter-clockwise direction, lookingfrom the bottom, over the contact bank. Magnet 68 likewise has anarmature 81 and a pawl 82 arran ed to engage ratchet wheel 66 to rotaterod 3 in the opposite direction. A flexible holding dog 83 exertssufficient pressure upon ratchet 66 to hold rod 7 3 in properpositionwhile being stepped around in either direction. Arranged on the underside of supporting shelf 64 and insulated therefrom is a circularconducting strip 84, concentrically disposed with respect to the axis ofthe releasing mechanism. A series of conducting segments 85 aresimilarly arranged along the arc of a circle in proximity to strip 84,being insulated from each other and from the supporting shelf 64. A pairof brushes 86 and 87, insulatedly mounted on ratchet wheel 65, arearranged so that the former makes engagement with the continuous strip84, while the latter successively engages the segments 85 duringrotation of the deposit pin restoring rod 73. The purpose of thesecircuit controlling members will be considered hereinafter.

A description of the operation of the.

group; thirdly, it must hunt automatically to n t e crossing point a tPa t ula incoming trunk 1 on which the call appears with the selectedoutgoing idle trunk 2; and lastly it must then deposit the circuitconnecting pin 8 associated with this crossing point. To accomplishthese functions, the group selecting series of impulses is sent toprimary magnet 35. Magnet 35 operates its stepping pawl 39 to advanceratchet 30 and gear 31 against the tension of spring 34. The gear 31acting upon. gear 20 operates to rotate carriage 17 together with bar 23and plunger 24 through an arc corresponding to a group of ten outgoingtrunks 2, 2 for each impulse sent to magnet 35. It is evident that, ifwhile carriage 17 and toothed bar 23 are thus being rotated in aclockwise direction as seen in Figs. 1 and 2, the gear member 11 remainsstationary with respect to the frame of the switch, rotation of thetoothed bar 23 about gear teeth 12 will cause said bar to besimultaneously thrust outwardly. This, however, is prevented by spring28, whose tension opposes the tendency of such a thrusting motion of bar23 sufiiciently to overcome the inertia and friction of thecomparatively lightmember 13, thereby causing said member 11 to rotateand maintain its normal relation with the teeth 'on bar 23. Rotation ofthe gear member 11 at this time is also in a clockwise direction, sothat the pawl 44 carried on ratchet 15 rides loosely over the teeth 13on said member 11. The holding dog 62 engaging the ratchet wheel 19serves to hold the operated parts in advanced position against thespring 34.

An operating circuit is next established for the secondary magnet 36which engages its pawl 41 with ratchet wheel 19 to advance the'samethrough the distance of one tooth for each energization of said magnet.Each step of ratchet 19 carries the bar 23 and its plunger 24 through anarc corresponding to the distance between two rows of outgoing trunkintersections. This operation con- 110 tinues until the plunger 24 ispositioned in radial alinement with an idle outgoing trunk 2 in theselected group, at which time the circuit of magnet 36 may be opened torender the same inactive. The holding dog 62 11 acts as in the case ofthe primary motion to retain the adjusted parts in their advancedposition against spring 34.

A circuit may now be closed for the tertiary magnet 37, which operatesthrough its 120 pawl 43 to step the ratchet 15 around in a clockwisedirection as seen in Fig. 1. The pawl 44, therefore, engages ratchetteeth 13, whereby the gear member 11 is forced to rotate in a similardirection. Since the 125 spring 34, acting through gears 31 and 20resists with considerable force any rotation of the carriage 17,rotation of the gear 12 consequently operates to slide the plunger ba .2out ar y agai st the ten ion of 130 spring 28. Hence, for eachenergization of magnet 87, the plunger 24 is advanced along the selectedtrunk 2 through a distance equal to that between two adjacent depositpins 8. As soon as the plunger 24 is stepped I thereby permits catch 51to drop into the particular notch 50 in bar 49 that corresponds to theadjusted position of plunger 24. As the rod 54 reaches its full upwardposition it engages and rotates a lever 88.

Lever 88 like the lever. 47 is securely fas-- tened to pivot pin 46 sothat rotation thereof by rod 54 causes a corresponding rotation of lever47. The lever 47 by rotating carries the supporting block 48 forwardslightly and since catch 51 is now engaging a notch 50, the plungeroperating bar 49 is simultaneously advanced with the block 48. Thismovement of bar 49 relative to the bar 23 operates the bell crank lever95 to press plunger 24 down against the selected deposit pin 8. Pin 8thereupon causes the springs 3 and 4 to respectively engage springs 5and 6 to complete the desired connection. The magnet 58 may now bedeenergized, whereupon the rod 54 by disengaging lever 88 permits spring26 to restore plunger 24 and plunger operating bar 49 to normalposition. 1

The switch having thus performed its function, a circuit is immediatelyestablished in any suitable manner for the release magnet 59. Magnet 59operates to withdraw both holding dogs 61 and 62. from engagement withratchets l5 and 19 respectively. Upon the withdrawal of dog 61 thespring 28 acts to pull the toothed bar 23 back through the channel 22 toits normal radial position. The dog 62 being also removed fromengagement with ratchet wheel 19, the spring 34 is at the same timeoperating through gears 31 and 20 to rotate carriage 17 and itsassociated parts back to thei normal rotary position. By such anarrangement a very simple releasing operation is made possible, it notbeing .I18C6Sf sary for the releasing movement to be completed in onedirection before it may begin in another direction as is theusual casein directively operated switches; The switch operating mechanism is nowrestored to its normal position and. is again available for I setting upother connections.

; After the conversation period has expired or if for any other reasonit becomes desir able to disable the established connection, therestoring mechanism operates as follows to restore the deposit pin 8 toits normal.

position. The stepping magnets 67 and 68 may be arranged to operate therestoring rod 73continuously forth and back over the contact bank,magnet 67 acting first to step the rod to its extreme forward position,and

magnet 68 thereupon acting to step it back agaln. As soon then asltbecomes necessary to restore the operated deposit pin 8, adiscriminating condition may be placed on the particular conductingsegment 85 individual to the trunk circuit 2 with which the oper atedpin 8 is associated, there being a seg'-' ment 85 fo each of the onehundred outgo-. ing trunks 2. l/Vhen the brush 87 arrives on.

this identified segment 85, suitable circuit means may be operated to.open the cir cult of the magnet 67 or 68 as the case may be. At thesametime the magnet .80 is momentarily energized, and by attracting itsarmature 78 rotates the rod 78. The apron 74 is thereby carried intoengagementwith the deposited pin 8 and the latter is restored to normal.Either the magnet 67 or 68 may now be operated to again start the continuous movement of the restoring mechanism.

lVhile in the drawing the switch disclosed illustrates a contact bank inwhich two-con' ductor trunks are used, it is apparent that of inco ingcircuits and a plurality of out goin circuits terminating in saidcontact bank, a plurality or" contact making members, each adapted toestablish a connection between one of the incoming and one of theoutgoing circuits, a switching mechanism arranged for a plurality ofselective movemerits, means for operating said mechanism toselect one ofsaid contact making members, and means for operating theselected contactmaking member.

2. Ina. switch, a contact bank, a plurality of incoming circuits and. aplurality of outgoing circuits terminating in said contact bank,'aplurality of contact-making members each adapted to establish aconnection between one of saidincoming circuits and mechanism arrangedfor a plurality'ot'selective movements, means for operating saidmechanism to select one of said comet-man ing members, means.foroperating the selected contact-making members, and means forrestoring the switching mechanism to its normal position.

3. In a switch, a contact bank, a plurality of incoming circuits and aplurality of outone of said, outgoing circuits, a..switchi;ng

of incoming circuits and a plurality of outgoing circuits terminating insaid contact bank, a plurality of contact-making members each adapted toestablish a connection between one of said incoming circuits and one ofsaid outgoing circuits, a switching mechanism arranged for a pluralityof selective movements, means for operating said mechanism to select oneof said contactmaking members, means for operating the selectedcontact-making member, means for restoring the switching mechanism toits normal position, and means for restoringthe selected contact-makingmember to its normal position.

5. In a switch, a contact bank, a plurality of incoming circuits and aplurality or" outgoing circuits appearing in said contact bank, aplurality oi' contact making members, each adapted to establish aconnection between one of the incoming and one of the outgoingcircuits,a switching device, means for advancing said device in a plurality ofselective movements to select any one of said contact making members,means for operating the selected contact making member, and means forreleasing the switching device, to normal while said contact makingmember remains in its operated position.

6. In a switch, a contact tank, a plurality of incoming circuits and aplurality of outgoing circuits terminating in said contact bank, saidcircuits being arranged such that each incoming circuit has a crossingpoint with each outgoing circuit, a switching device, means forselectively operating said device in a plurality of directions to selectone of said crossing points, and means for establishing a connectionbetween the circuits at the selected crossing point.

7. In a switch, a contact bank,'a plurality of incoming circuits and aplurality of outgoing circuits terminating in said contact bank,saidcircuits being arranged such that each incoming circuit has a crossingpoint with each outgoing circuit, contact members at each of saidcrossing points for establishing a connection between an incoming and anoutgoing circuit, a switching device, means for advancing said device toselect any one of said crossing points, means for operating the contactmembers at the selected crossing point, and means for restoring saidswitching device to normal.

8. In a switch, a contact bank, two groups of trunks terminating in saidcontact bank, said trunks being arranged such that each trunk of onegroup has a-orossing point with each trunk of the other group, contactmembers at each crossing point for establishing connection between atrunk of one group andv a trunk of the other group, a step-bystepoperated switching device, means for advancing said switching device toselect any one of said contact members, means for operating said deviceto operate the selected contact member, means for restoring theswitching device to normal, and step-by-step actuated means forrestoring an operated contact member to normal position.

9. In a switch, a contact bank, a plurality of incoming trunks and aplurality of outgoing trunks terminating in said contact bank, aplurality of contact making members, each ,adapted to establish aconnection between one of the incoming and one of the outgoing circuits,said members being arranged ingroups, a switching device, means foradvancing said device to select a group, means for advancing said deviceto select a contact making member in the group, means for operating theselected contact making member, and means for restoring said switchingdevice to normal position.

1.0. In a switch, a contact bank, a plurality of incoming trunks and aplurality of outgoing trunks terminating in said bank, a plurality ofcontact making members, each adapted to establish a connection betweenone of the incoming and one of the outgoing circuits, said members beingarranged in groups and subgroups, a switching device, means foradvancing said device to select a group, means for advancing said deviceto select a subgroup, means for advancing said device to select acontact making member in the subgroup, means for operating said. member,means for thereupon restoring the swtiching device to normal, and meansfor restoring an operated contact making member to its normal position.

11. In a switch, a contact bank, a pluralityof incoming trunks and aplurality short steps to select a subgroup, means for further movingsaid device to select a contact set in the subgroup, means for operatingsaid set, and means for then restoring the switching device to itsnormal position.

12. In a switch, a contact bank, a plurality I of incoming trunks and aplurality of outgoing trunks terminating in said bank, said trunks beingarranged such that each incoming trunk has a crossing point with eachoutgoing trunk, a contact set at each crossing point for connecting anincoming trunk to an outgoing trunk, a deposit pin for operating eachcontact set, a plunger, means for selectively advancing said plunger toselect any one of said deposit pins, means for operating said plunger tooperate the selected deposit pin, means for restoring said plunger toits normal position, and means for restoring an operated deposit pin.

18. In a switch, a contact bank comprising a plurality of sets of springcontacts, said sets of contacts being arranged in groups and subgroups,a switching device arranged to be advanced in a plurality of selectivemovements to select and operate a desired contact set, and means forrestoring said device to normal position while maintaining the contactset operated.

14:. In a switch, a contact bank comprising aplurality of sets of springcontacts, a pin associated with each of said contact sets, a plunger,means for advancing said plunger step-by-step in a plurality ofselective movements to select a set of contacts, means for operatingsaid plunger to depress the pin associated with the selected set toclose the contacts thereof, and means for restoring a depressed pin toits normal position.

15. In a switch, two groups of conductors, said conductors beingarranged such that any conductor inone group may be connected to anyconductor in the other group, a switching device, means for operatingsaid device in arcuate and radial selective movements to select adesired conductor in each of said groups, means for establishing aconnection between the selected conductors, and means for restoring saidswitching device to normal position.

16. In a switch, a contact bank comprising a plurality of sets ofcontact members arranged in a plurality of arcuate rows and radial rows,said contact members arranged to lock in their operated positions, aswitching mechanism comprising a bar rotatable into operable relation toany of said radial rows individually and movable radially over saidradial rows, an operating plunger for said contact member carried bysaid bar, an electromagnetic step-by-step mechanism for selectivelyrotating said bar and plunger into alinement with a desired radial rowof contact members, a second electromagnetic step-by-step mechanism forselectively moving said bar and plunger radially into operable relationwith a desired contact mem-' ber, means for moving said plunger tooperate said contact member, means for restoring said plunger to normal,means for restoring said switch mechanism to its normal position uponcompletion of an operation, and a common restoring means for saidcontact members.

17. In a switching mechanism, a row of contact operating members, a barmovable longitudinally .over' said contact operating members, a plungeron said bar for operating said contact operating members individually,an operating bar for said plunger arranged parallel with saidfirst-mentioned bar and movable therewith, means for moving saidfirst-mentioned bar radially to position said plunger int-o operablerelation with a contact operating member, means operable to move saidoperating bar to effect operation of said plunger, said last-mentionedmeans being operable when said plunger is in any of its operablepositions.

18. In a switching mechanism, a plurality of rows of contact operatingmembers, means for operating said contact operating membersindividually, a restoring device for said contact operating memberscomprising a rod, an apron on said rod, said rod movable into operablerelation to any of said rows of contact, members individually, meansfor'moving said rod into operable re lation to a row of contact members,and means for rotating said rod to effect a movement of said apron torestore an operated contact member to normal. r

In witness whereof I hereunto subscribe my name this 8th day of May, 'A.D. 1918.

JAMES L. MGQUARRIE.

